Inspection Procedure 33: Proportional Oxygen Sensor System










OPERATION



  • Power is supplied to the heater power terminal (terminal No. 4) of the proportional oxygen sensor connector from the engine-ECU (terminal No. 63, terminal No. 75 and terminal No. 87).
  • The heater (terminal No. 3) of the proportional oxygen sensor connector is controlled by the power transistor in the engine-ECU (terminal No. 146).
  • The oxygen concentration signal is inputted to the engine-ECU (terminal No. 62) from the proportional oxygen sensor output terminal (terminal No. 6).
  • The power voltage is earthed to the engine-ECU (terminal No. 74) from the proportional oxygen sensor (terminal No. 2).
  • The pump current is inputted to the engine-ECU (terminal No. 61) from the proportional oxygen sensor output terminal (terminal No. 1).
  • The lambda value signal is inputted to the engine-ECU (terminal No. 73) from the proportional oxygen sensor output terminal (terminal No. 5).

FUNCTION



  • The proportional oxygen sensor is used to detect the oxygen concentration in the exhaust gas.
  • The engine-ECU calculates the quantity and start of extended injection based on this output signal.
  • Proportional oxygen sensor heater control the current applied to the proportional oxygen sensor heater circuit in accordance with signals from the engine-ECU.

PROBABLE CAUSES



  • Failed proportional oxygen sensor heater
  • Open/short circuit or harness damage in proportional oxygen sensor circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-15 proportional oxygen sensor connector

Q. Is the check result normal?
Go to Step 2 .
Repair or replace the connector.

STEP 2. Perform voltage measurement at B-15 proportional oxygen sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 4 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 6 .
Go to Step 3 .

STEP 3. Connector check: B-17 engine-ECU connector.

Q. Is the check result normal?
Go to Step 4 .
Repair or replace the connector.

STEP 4. Check harness between B-15 (terminal No. 4) proportional oxygen sensor connector and B-17 (terminal No. 63, terminal No. 75 and terminal No. 87) engine-ECU connector.

  • Check power supply line for open/short circuit.

Q. Is the check result normal?
Go to Step 5 .
Repair the damaged harness wire.

STEP 5. Check trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU.
Intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 6. Connector check: B-17 engine-ECU connector

Q. Is the check result normal?
Go to Step 7 .
Repair or replace the connector.

STEP 7. Check harness between B-15 (terminal No. 4) proportional oxygen sensor connector and B-17 (terminal No. 63, terminal No. 75 and terminal No. 87) engine-ECU connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Check harness between B-15 (terminal No. 3) proportional oxygen sensor connector and B-16 (terminal No. 146) engine-ECU connector.

  • Check earthing line for damage.

Q. Is the check result normal?
Go to Step 9 .
Repair the damaged harness wire.

STEP 9. Check harness between B-15 (terminal No. 2) proportional oxygen sensor connector and B-17 (terminal No. 74) engine-ECU connector.

  • Check earthing line for open circuit and damage.

Q. Is the check result normal?
Go to Step 10 .
Repair the damaged harness wire.

STEP 10. Check harness between B-15 (terminal No. 6) proportional oxygen sensor connector and B-17 (terminal No. 62) engine-ECU connector.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 11 .
Repair the damaged harness wire.

STEP 11. Check harness between B-15 (terminal No. 5) proportional oxygen sensor connector and B-17 (terminal No. 73) engine-ECU connector.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 12 .
Repair the damaged harness wire.

STEP 12. Check harness between B-15 (terminal No. 1) proportional oxygen sensor connector and B-17 (terminal No. 61) engine-ECU connector.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 13 .
Repair the damaged harness wire.

STEP 13. Replace the proportional oxygen sensor.

  • After replacing the proportional oxygen sensor, re-check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU.
The check is end.